POLLINATION AND STERILITY 307 



273. The quince is reported by Waite to be nearly as 

 fruitful when self-pollinated as when cross-pollinated. 



274. The apple. — As a class, the apple is inclined to be 

 self-sterile although a number of varieties are known to be 

 at least partially self -fertile. In contrast with the grape, the 

 sterility is, according to Kraus, "due almost wholly to em- 

 bryo abortion," and Knight ^ says also to lack of pollen- 

 tube growth. From a practical standpoint, it is always bet- 

 ter to have mixed plantings than a solid block of one variety, 

 although the latter may be successful under some conditions. 



Waugh worked with eighteen varieties of apple commonly 

 grown in New England and reported them all to be practi- 

 cally self-sterile. Out of 258(3 blossoms covered, only three 

 apples set, or l/lO of 1 per cent. 



Lewis and Vincent reported that of eighty-seven varieties 

 tested, fifty-nine were self-sterile, fifteen self-fertile, and thir- 

 teen partially self-fertile." 



Waite states that "The varieties of apples are more in- 

 clined to be sterile to their own pollen than the pears. With 

 the former, in the great majority of cases, no fruit resulted 

 from self-pollination." 



Alderman ^ investigated the Rome Beauty, York Impe- 

 rial, and Wagener for a period of three years, with the follow- 

 ing results: 



iProc. Soc. Hort. Sci. 1917. 



2 Ore. Agr. Exp. Sta. Bull. 104. 1909. 



3 Loc. cit. 



